CAMP-regulated Protein Lysine Acetylases in Mycobacteria

Subhalaxmi Nambi,Nirmalya Basu,Sandhya S Visweswariah

doi:10.1074/jbc.m110.118398

Subhalaxmi Nambi, Nirmalya Basu + Show 1 more

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https://doi.org/10.1074/jbc.m110.118398

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Abstract

Cyclic AMP synthesized by Mycobacterium tuberculosis has been shown to play a role in pathogenesis. However, the high levels of intracellular cAMP found in both pathogenic and non-pathogenic mycobacteria suggest that additional and important biological processes are regulated by cAMP in these organisms. We describe here the biochemical characterization of novel cAMP-binding proteins in M. smegmatis and M. tuberculosis (MSMEG_5458 and Rv0998, respectively) that contain a cyclic nucleotide binding domain fused to a domain that shows similarity to the GNAT family of acetyltransferases. We detect protein lysine acetylation in mycobacteria and identify a universal stress protein (USP) as a substrate of MSMEG_5458. Acetylation of a lysine residue in USP is regulated by cAMP, and using a strain deleted for MSMEG_5458, we show that USP is indeed an in vivo substrate for MSMEG_5458. The Rv0998 protein shows a strict cAMP-dependent acetylation of USP, despite a lower affinity for cAMP than MSMEG_5458. Thus, this report not only represents the first demonstration of protein lysine acetylation in mycobacteria but also describes a unique functional interplay between a cyclic nucleotide binding domain and a protein acetyltransferase.

Highlights

Industrial Research, Government of India. 2 Recipient of a Junior Research Fellowship from the Council of Scientific and Industrial Research, Government of India. 3 To whom correspondence should be addressed: Dept. of Molecular mechanisms underlying the production, utilization, and degradation of cAMP by M. tuberculosis may provide avenues for the identification of novel targets for drug development [8]
The genomes of non-pathogenic mycobacteria, such as Mycobacterium smegmatis, encode multiple nucleotide cyclase genes, which could account for the high intracellular cAMP levels found in these bacteria [9]. cAMP levels are modulated by various stress conditions in M. smegmatis [9], suggesting that cAMP participates in signaling within the bacterial cell, mediating its action by downstream effectors
Alignment of the N-terminal cNMP binding domain to the regulatory subunit of protein kinase A (PKA) showed that residues critical for cAMP binding in PKA (20 –21) are conserved in Rv0998 and its ortholog in M. smegmatis, MSMEG_5458 (Fig. 1A)

Summary

Introduction

Industrial Research, Government of India. 2 Recipient of a Junior Research Fellowship from the Council of Scientific and Industrial Research, Government of India. 3 To whom correspondence should be addressed: Dept. of Molecular mechanisms underlying the production, utilization, and degradation of cAMP by M. tuberculosis may provide avenues for the identification of novel targets for drug development [8]. The cNMP domain in these proteins is fused to, and regulates the activity of, a GNAT-like protein acetyltransferase, which acetylates the epsilon amino group of a lysine residue in a Universal Stress Protein (USP, MSMEG_4207).

Results

Conclusion